David R. Thompson1

Bo-Cai Gao2

Robert O. Green1

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA2 Naval Research Laboratory, Washington, DC

Copyright 2015 California Institute of Technology. All Rights Reserved.

US Government Support Acknowledged.

Radiometric calibration and

atmospheric correction

6/18/2015 david.r.thompson@jpl.nasa.gov 1

6/18/2015 david.r.thompson@jpl.nasa.gov 2

Raw DNs

Radiance (W/nm/sr/cm2)

Reflectance (HDRF)

Part 1: Radiometric Calibration

Part 2: Atmospheric Correction

NASA/JPL Portable Remote Imaging Spectrometer (PRISM)

A motivating example

from PRISM

6/18/2015 david.r.thompson@jpl.nasa.gov 3

0.4 0.45 0.5 0.55 0.6 0.650

0.002

0.004

0.006

0.008

0.01

Rrs

0.4 0.45 0.5 0.55 0.6 0.65

−2

−1

0

1

2

x 10−3

Wavelength (microns)

Res

iduu

m

Wavelength (microns)

PRISM

flightline

M0 Buoy

retrieved

Pajaro River

retrieved

Wavelength (microns)

In situ

In situ

D. R. Thompson, F. Siedel, B.-C. Gao, M. Gierach, R. Kudela, R. O. Green, P. Mouroulis. Optimizing Solar

Irradiance for Coastal Spectroscopy. Geophysical Research Letters (2015, in press).

0.4 0.45 0.5 0.55 0.6 0.650

0.002

0.004

0.006

0.008

0.01

Rrs

0.4 0.45 0.5 0.55 0.6 0.65

−2

−1

0

1

2

x 10−3

Wavelength (microns)

Res

idu

um

In-situ data courtesy Raphe Kudela, UCSC

0.4 0.45 0.5 0.55 0.6 0.650

0.002

0.004

0.006

0.008

0.01

Rrs

0.4 0.45 0.5 0.55 0.6 0.65

−2

−1

0

1

2

x 10−3

Wavelength (microns)

Res

iduu

m

Two issues…

6/18/2015 david.r.thompson@jpl.nasa.gov 4

UV falloffSpikes?

Wavelength (microns)

Part 1: Radiometric

calibration

6/18/2015 david.r.thompson@jpl.nasa.gov 5

6/18/2015 david.r.thompson@jpl.nasa.gov 6

Remove dark current levels

Remove electronic

effects

Apply radiometric calibration

Apply flat fieldFind

zero

Translate to Radiance

Raw DNs

Radiance (W/nm/sr/cm2)

NASA/JPL Portable Remote Imaging Spectrometer (PRISM)

Radiometric Calibration

Calibration challenges:

radiometry

6/18/2015 david.r.thompson@jpl.nasa.gov 7

0 500 1000 1500 2000 25000

0.5

1

1.5

2

2.5

3x 10

−5

Wavelength (nm)

W/(

cm2 n

m)

Typical red-rich calibration source

Spectral

response

affects the

estimated

radiometry

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0.4 0.5 0.6 0.7 0.8 0.9 1

−4

−2

0

Panel scan: ang20140610t232914

PS

F (

Lo

g s

cale

)

0.4 0.5 0.6 0.7 0.8 0.9 10

5000

10000

DN

s

0.4 0.5 0.6 0.7 0.8 0.9 10.85

0.9

0.95

1

1.05

Wavelength (microns)

Ratio

Illuminated panel

measurement

Deconvolved

Deconvolved

Measured

Spectral response

having non-Gaussian

tails

Part 2: Atmospheric

correction

6/18/2015 david.r.thompson@jpl.nasa.gov 9

6/18/2015 2JPL/Caltech PROPRIETARY — Not for Public Release or Redistribution. The technical data in this document is controlled under the U.S. Export Regulations, release to foreign persons may require an export authorization.

0.38 0.4 0.42 0.44 0.46 0.48 0.5 0.52 0.54 0.56 0.580

0.5

1

Wavelength (micron)

Val

ue

PRISM sampling

TNO2

TO3

TuT

d

s

ra

Irradiance 1250

2500

Irra

dia

nce

W/m

2 /mm

6/18/2015 david.r.thompson@jpl.nasa.gov 11

Gas absorption terms

Path reflectance

Optimizing irradiance estimates

• Hypothesis: fine spectral sampling (~3nm) causes sensitivity to sampling of the solar irradiance (and intrinsic uncertainty)

• Solution: modify an irradiance estimate using a smooth in-scene reference(here, a concrete surface)

6/18/2015 david.r.thompson@jpl.nasa.gov 12

Optimizing irradiance estimates

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Penalize difference vs. smoothed reflectance

Penalize large perturbations

LevenbergMarquardt

Agreement

with in situ Rrs

is improved

D. R. Thompson, F. Siedel, B.-C. Gao, M. Gierach, R. Kudela, R. O. Green, P. Mouroulis. Optimizing Solar Irradiance for Coastal Spectroscopy. Geophysical Research Letters (2015, in press).

6/18/2015 3JPL/Caltech PROPRIETARY — Not for Public Release or Redistribution. The technical data in this document is controlled under the U.S. Export Regulations, release to foreign persons may require an export authorization.

Wavelength (microns) Wavelength (microns)

M0 Buoy,

Rrs retrieval using different

solar irradiance spectra

Pajaro River

Aerosols are a persistent challenge

In-situ data courtesy Sherry Palacios and Liane Guild, NASA Ames; Raphe Kudela, UCSC

In situ

remote

Concluding thoughts

• Ocean observations place extreme

requirements on both calibration and

atmospheric correction

• Is there a common root cause to both

issues (far tails of the SRF)?

• Underscores need for spectral uniformity

6/18/2015 david.r.thompson@jpl.nasa.gov 16

Thanks

• The PRISM team, including Zakos

Mouroulis, Byron Van Gorp, Mark

Helmlinger, Scott Nolte, Sarah Lundeen

• Felix Seidel, Heidi Dierssen, Michelle

Gierach, John Fontenla, Raphe Kudela,

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